Abstract PS3-01-27: Association between adherence to the mediterranean dietary pattern and PAM50-derived breast cancer proliferation and recurrence risk scores. Exploratory analysis from the Epigeicam study

Abstract Background: There is growing evidence supporting the benefits of the Mediterranean diet in breast cancer (BC) prevention, but their contribution to prognosis remains unclear. Our objective is to investigate whether adherence to the Mediterranean dietary patterns before diagnosis is associated with the risk of BC recurrence and tumor proliferation in an exploratory cohort of the multicenter case-control EpiGEICAM study. Methods: Transcriptome-wide gene expression was assessed using the nCounter Breast Cancer 360 panel (NanoString). Formalin-fixed paraffin-embedded tumor tissues from an exploratory cohort of 89 pre- or perimenopausal BC patients from the EpiGEICAM study were used. The PAM50 gene expression signature was employed to classify tumors into the gold-standard BC intrinsic molecular subtypes, and to compute both the PAM50 risk of recurrence (ROR) and PAM50 proliferation scores. Dietary patterns over the five years prior to diagnosis were identified in the control population of the EpiGEICAM study, applying principal components analysis without rotation of the variance-covariance matrix over 26 inter-correlated food groups. The association between adherence to Mediterranean dietary patterns and both ROR and proliferation scores was analyzed using linear regression models with continuous outcomes. All models were adjusted for age and adherence to a Western dietary pattern, with additional adjustment for PAM50 molecular subtype in the proliferation score analysis. Results: The mean age was 44 years and 28% had a family history of BC. Regarding molecular subtypes, 49.4% corresponded to Luminal A, 22.5% to Luminal B, 13.5% to HER2-enriched and 14.6% to Basal-like subtype. High adherence to the Mediterranean dietary pattern was observed in 56% of participants, with higher prevalence among women with Luminal A and Luminal B subtypes. The mean ROR score was 51 (95%CI=46-57) in women with low adherence to the Mediterranean diet, and 46 (95%CI=40-51) in those with high adherence. Mean proliferation scores were 4.8 (95%CI=4.6-5.1) and 4.5 (95%CI=4.3-4.8), respectively. Although no statistically significant associations were observed, women with high adherence to the Mediterranean dietary pattern showed lower mean ROR score (β=-5.8; 95%CI=-14.0-2.5) and a reduced proliferation score (β=-0.14; 95%CI=-0.40-0.12) compared to those with low adherence. Conclusion: The present EpiGEICAM exploratory analysis showed that adherence to a Mediterranean dietary pattern prior to diagnosis may be associated with lower breast cancer PAM50 proliferation and risk of recurrence scores. Studies with larger sample sizes are needed to confirm these results and to clarify the effect of the Mediterranean diet on the biology and prognosis of this tumor. Citation Format: V. Lope, P. Fernández, Á. Guerrero-Zotano, P. Sánchez-Rovira, A. Antón-Torres, M. Benavent-Viñuales, J. Baena-Cañada, S. Antolín, M. Muñoz, L. Paris, J. Chacón, C. Olier, S. González, J. García-Sáenz, Á. Jimenez-Arranz, A. Oltra, J. Brunet, M. Marin-Alcala, A. De Juan, B. Pérez-Gómez, R. Rincón, R. Caballero, B. Bermejo, M. Martín, M. Pollan. Association between adherence to the mediterranean dietary pattern and PAM50-derived breast cancer proliferation and recurrence risk scores. Exploratory analysis from the Epigeicam study [abstract]. In: Proceedings of the San Antonio Breast Cancer Symposium 2025; 2025 Dec 9-12; San Antonio, TX. Philadelphia (PA): AACR; Clin Cancer Res 2026;32(4 Suppl):Abstract nr PS3-01-27.